Glass grinding apparatus



July 27, 1937. F, B, WALDRON 2,088,392

NG APPARATUS Original Filed Feb. 8, 1935 Patented July 21, 1937.

, 2,088,392 GLAss Gamme. APPARATUS Frederic Barnes Waldron, Prescot, England, assignor to Pilkington Brothers Limited, Liver-- Dl, England, a British company Original application February 8, 1935, Serial No. 5,507. Divided and this application April 15, 1937, Serial No. 137,077. In Belgium February 1 Claim.

This invention relates to grinding tools for grinding a travelling strip of glass, and has for its object a grinding tool in which the operative surface is so disposed as to produce a atter surface on the glass and to grind more eiciently. This application is a division of application 5507 filed February 8, 1935.

'Ihe operative surface of grinding tools, used in a continuous grinding machine on a travelling strip of glass, and supplied with abrasive at the centre of the tools, is commonly composed of the surfaces of blocks, formed by two sets of grooves, one set leading the abrasive outwardly from the centre, while the other set is circular, and concentric with the axis of the tool.

The outwardly leading grooves serve to enable abrasive supplied at the centre to reach the outerparts of the tool, and the circular grooves serve for the renewal of the spent abrasive. When a quantity of abrasive reaches the operative surface of a block, it travels to the outer edge of this block while performing grinding work. After doing a certain amount of grinding, it loses its efficiency as an abrasive. Its path from the inner to the outer edge of the block, that is to say, from one circular groove to the next, is such that, before the abrasive becomes spent, it reaches a circular groove and there becomes mixed with fresh abrasive,`so that fresh abrasive reaches the'operative surface of the next block outwards.

In the following specification, grooves serving mainly to lead the abrasive outwardly will be termed spreading grooves, and grooves serving mainly to provide fresh abrasive will be termed mixing grooves. Thus, in the ordinary form of grinding tool, the spreading grooves are radial and the mixing grooves circular.

Now the glass produced by grinding tools of the above described customary form, is sufficiently fiat for many commercial purposes, but certain irregularities in atness are produced which render the glass unsuitable for certain purposes.

If the annular grinding surface be regarded as divided up into narrow concentric rings, it leas been found that irregularities in flatness are produced when the area of grinding surface in any one ring differs largely from that in the adjacent rings. Now the condition that the area of grinding surface in any one ring should not differ largely from that in the adjacent rings can be fulfilled by making the mixing grooves elliptical or eccentric, with suitable eccentricity. A grinding tool with such grooves, however, is

tool for operating on travelling flat glass has a solid outer rim and two sets of intersecting grooves, the two sets being inclined respectively at different angles, between 0 and ninety degrees to the radius, so that vthe outer end of veach groove is in advance (with reference to the direction of rotation) of its inner end, and a plurality of four-sided blocks of which the sides are formed by the said two sets of grooves two of the sides thereof facing their direction of travel at such angles that the outer end of each is in advance ofthe inner.

'I'he accompanying drawing represents a plan view of the operative surface of a grinding tool according to the invention.

The discv l, with central hole 2, through which abrasive is supplied, has fixed to it, or formed on it, blocks 3. -The disc turns in the direction shown by the arrow. The blocks 3 4are formed by two sets of grooves 4 and 5. The spreading grooves 4 are inclined to the radius, so that their outer portions are in advance of the inner portions. The mixing grooves 5 are at a substantially greater inclination in the same direction. 'I'he grooves terminate before the outer edge of the disc, leaving a solid rim 6. f The mixing grooves 5 are curved, While the spreading grooves are straight, but have staggered portions.

The blocks formed by the two sets of grooves (excepting the innermost blocks and the outer rim) have two leading faces inclined to the radius, so that the outer end of each such face is in advance of the inner end.

When the blocks are so formed, by two sets of grooves, the abrasive is evenly distributed, and the abrasive nowhere has an unduly long operative path before becoming mixed with fresh abrasive and so that no concentric ring of the tool differs largely in grinding area from the adjacent rings.

Since, in the customary form of tool with concentric mixing grooves, there are usually three rings having no grinding area at all, each between rings having 60% to 70% of grinding area, the advantage of the arrangements according to the invention is clear.

The invention includes the case where the I:

' operative surface are in advance of the edges on the operative surface. Thereby the abrasive is forced upwards to the operative surface.

Having described my invention, I declare that what I claim and desire to secure by Letters Patent is:-

Disc grinding tool for operating on travelling fiat glass, having a solid outer rim and two sets of intersecting grooves, the two sets being inclined respectively at diierent angles, between 0 and ninety degrees to the radius, so that the outer end of each groove is in advance (with reference to the direction of rotation) of its ln ner end, and a plurality of four-sided blocks of which the sides are formed by the said two sets of grooves, two of the sides thereof facing their direction of travel at such angles that the outer end of each is in advance of the inner.

FREDERIC BARNES WALDRON. 

